This invention relates to the field of waveform analysis, and more particularly to the field of analyzing the relative amount of time that a repetitive electrical signal spends at each of the voltage levels that it assumes.
Histogram displays representing the waveform profile or relative amount of time that a repetitive electrical signal spends at each of the voltage levels that it passes through have been used in the analysis of waveforms for some time Once this waveform profile data is available, numerous calculations of other waveform parameters can be made directly from this data, without further need for the actual waveform data itself. The minimum, maximum, mean, median, peak-to-peak, topline, baseline, and the root-mean-square values can all be calculated from the waveform profile (or histogram) data. And, once the topline and baseline are known, overshoot and other aberrations can also be quantified.
The mostly commonly used method for generating waveform profile data, or a histogram, has been based on sampling the signal a number of times, then sorting those samples into amplitude bins and counting the number of samples that fall into each bin. The actual sampling is typically performed by a high speed A/D (analog-to-digital) converter. There are, however, limits to how fast sequential, real-time sampling can be performed. There is also a limitation to how accurately one can know when the sample was taken, i.e., timing resolution.
If equivalent time sampling is used instead of real-time sampling, higher frequency signals can be analyzed, but the time required to complete the acquisition of the necessary data is considerably increased.
The quality of histograms created from sampled data is also limited by the number of points sampled and stored. To the extent that the record length is not long enough, the statistical basis for the histogram data is limited.
What is desired is an alternative approach to establishing a waveform profile, one that works effectively at the highest possible frequencies, that produces waveform profiles with a sound statistical basis in a minimum amount of time, and that is suitable for a counting/timing oscilloscope or other instrument without high-speed digitizing capabilities.